1021-4437/05/5203- © 2005
Russian Journal of Plant Physiology, Vol. 52, No. 3, 2005, pp. 365–373. From Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 412–420.
Original English Text Copyright © 2005 by Sammour.
Glycinins are predominant storage proteins in soy-
bean seeds. They account for more than 20% of the
seed dry weight in some cultivars, being produced pri-
marily in cotyledon cells where they are sequestered
within subcellular organelles called protein bodies [1–4].
As isolated from seed extracts, glycinins are oligomers
consisting of six similar subunits [5–7]. The properties of
these subunits have been reviewed extensively [2, 8–13].
Glycinin subunits accumulate rapidly during
embryogenesis, and this accumulation is associated
with dramatic changes in the prevalence of glycinin
mRNAs . Glycinin mRNAs begin to accumulate
early in embryogenesis, are highly prevalent during the
mid-maturation stage, and decay prior to seed dor-
mancy [14–16]. The accumulation stage and decay of
these mRNAs is regulated in part by transcriptional
processes similar to those that regulate other seed pro-
tein mRNAs [15, 17, 18].
 characterized structure, organiza-
tion, and expression of genes that encode the soybean
glycinins. Five genes encode predominant glycinin
subunits found in soybeans. Five genes have diverged
into two subfamilies that are designated as Group-1 and
Group-2 glycinin genes. The genes in Group-1 include
, while the genes in Group-2 include
[1, 17]. Recently, Beilinson
identiﬁed two new genes: a glycinin pseudo-gene,
and a functional gene,
. Even though the amino acid
sequence of the glycinin subunit G7 is related to other
ﬁve soybean 11S glycinin subunits, it does not ﬁt into
either the Group-1 (Gl, G2, and G3) or the Group-2 (G4
and G5) glycinin subunit families.
 developed an
that results in the self-assembly of Group-2 proglycinin
subunits into those resembling natural subunits found
in the endoplasmic reticulum. The self-assembly of
Group-2 proglycinin into trimers required post-transla-
tion cleavage before they are assembled into hexamers
similar to those isolated from the proteins bodies of
mature seeds [2, 13, 20]. The ability to synthesize and
assemble glycinin complexes
is a useful tool for
attempts to engineer subunits with an improved nutri-
tional quality [21–24], as well for identiﬁcation of
regions in the subunits crucial for oligomer formation
[6, 25, 26].
Because of the high concentration of the glycinin,
its major contribution to the nutritional properties of
soybean proteins, and its effect on the functional prop-
erties of food products made from beans, it has been
targeted for genetic manipulation to improve soybean
nutritional quality. The observation that G2, the subunit
rich in sulfur amino acids, does not self-assemble
could mean that a modified G2 expressed at a high
level will not assemble efﬁciently in protein bodies
. While it remains to be demonstrated that the
is equivalent to that which occurs
, an alternate and better strategy to improve nutri-
tional quality may be to alter those subunits capable of
self-assembly, namely G4 subunit. This study, there-
fore, was carried out to construct three bacterial
mutants containing an increased amount of methionine
Molecular Manipulation and Modification of the
Encoding Glycinin Subunits in Soybean Seeds
R. H. Sammour
Department of Botany, Faculty of Science, Tanta University, P.O. Box 2, Tanta, Egypt;
Received March 26, 2004
genes encoding glycinin subunits were molecularly manipulated and modiﬁed to
test the possibility of increasing the nutritional value of soybean seed proteins. With the respective recombinant
pSP65/G2HG4, pSP65/G4HG2, pSP65/248Metl, pSP65/248Met2,3
translation was used to produce (i) chimeric proteins consisting of reciprocally exchanged acidic and basic
domains of the G2 and G4 subunits, and (ii) G4 point mutants with increased number of methionine residues.
The ability of the recombinant proteins to assemble into proper quaternary structures was inspected by sucrose
gradient fractionation. The produced data could provide valuable clues for the potential improvement of the
genetically modiﬁed crops.
Key words: Glycine max - cloned cDNA - glycinin subunit G4 - in vitro translation - mutagenesis -
This article was submitted by the author in English.